2) All image sizes are defined in functions.php – the default fullwidth size is 930px width (and “unlimited” height based on the aspect ratio) and the page/sidebar template will use the same image but scale it down to the content container width.

Thanks. Can I upload an image that is e.g. 400 px wide and then right-align it and have text show to the left of the image. Or should I rather upload an image that is 930 px wide in total with included white space beyond the 400 px width of the photo?

If you have a sidebar, the slideshow will be constrained to a 610px wide size. However, it will still use the 930px wide image size unless that width is changed in your functions.php. IE – The theme doesn’t create a different image for use in the slideshow specific for use on pages with a sidebar it just constrains the larger full size image to the smaller container size.